http://land-water-air-space-vehicles-crafts.blogspot.ca/2016/02/how-to-calculate-battery-charging-time.html
How to Calculate Battery Charging Time via Solar Panel
Given:
Kia Sportage 12 Volt Car Battery 60 AH (ampere-hour) capacity
ALLPOWERS solar charger 18 volts, 7.5 watts, 0.4 amperes max
Mono-crystalline silicon panel
* No-load voltage: 18-23VDC
* Load voltage: 18V
* Output current: 270-410 mAh (0.27A-0.4A)
* Size: 320 x 128 x 4mm / 12.6 * 5.0 * 0.12 inch
* Weight:0.323 kg / 11.4oz
Attention:
Unplug the charger at night, for it needs sunlight to charge devices
FACTORS AFFECTING BATTERY CHARGING TIME
- Battery state: the more the battery is discharged, the longer it takes to charge
- Battery rating: the more the battery AH capacity, the longer the charging time
- Charging rate: this is the Ampere rating of the charger (output current)
- Sun intensity: the clearer, brighter sky, the more voltage and more amperes from the sun
- Sun hours: amount of hours of sunlight during the day of the geographic location
- Charger efficiency: for mono-crystalline solar chargers, 85-90%
- Temperature: Colder temperatures means longer charging time
Assumptions:
Sun hours: 4 hours, average cloudy day
Location coordinates: Latitude = 48 N, Longitude = 123 W
Charging rate: average output current = (0.27A + 0.4A)/2 = 0.33 amps
Charger efficiency: 85%
Battery state of charge: 50%
12 Volt Battery State of Charge:
Volts — % Charged
12.6 —- 100 %
12.5 —- 90 %
12.4 —- 80 %
12.3 —- 70 %
12.2 —- 60 %
12.0 —- 50 %
11.9 —- 40 %
11.8 —- 30 %
11.6 —- 20 %
11.3 —- 10 %
10.5 —- 0 %
CHARGE TIME CALCULATION
Step 1: Calculate Average Daily Ampere-Hour of Charger
Ave Daily Ah = Ave Charging rate x Sun hours x Charger efficiency
Ave Daily Ah = 0.33 Amps x ( 4 hours/day ) x 0.85
Ave Daily Ah = 1 Ah/day
Step 2: Calculate Battery Capacity Energy Top Up Amount
Battery Top Up Amount = Battery Capacity x State of Charge
Battery Top Up Amount = 60 Ah x 50%
Battery Top Up Amount = 30 Ah
Step 3: Calculate Battery Charging Time
Battery Charging Time = Battery Top Up Amount/Ave Daily Ah
Battery Charging Time = 30 Ah/1 Ah per day
Battery Charging Time = 30 days (1 month)
Post time: Jan-03-2017